Impeller, air-sending apparatus, and cleaning machine

ABSTRACT

An impeller includes a main plate spreading radially with respect to the center axis, a plurality of blades provided on an upper surface of the main plate and arranged side by side in a circumferential direction, a shroud connected to tops of the plurality of blades and having an intake port that is an opening extending upward, and a mount portion provided on the upper surface of the main plate and positioned on an inner side with respect to a radially outer end of the main plate. The mount portion has a plurality of recesses each being depressed downward from an upper surface of the mount portion and extending in a direction away from the center axis.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese PatentApplication No. 2017-138108 filed on Jul. 14, 2017. The entire contentsof this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to an impeller, an air-sending apparatus,and a cleaning machine.

2. Description of the Related Art

An impeller included in an electric air-sending apparatus is known. Theimpeller included in the electric air-sending apparatus is fastened to amotor shaft with a nut. The impeller includes a front shroud, a rearshroud, and a plurality of blades.

The front shroud has an umbrella-like shape and is provided on theair-inlet side. The rear shroud is a flat plate and is provided acrossan air-passage space in the impeller from the front shroud. Theplurality of blades are held between the front shroud and the rearshroud. Air flows from a central part of the front shroud into theimpeller. The air thus flowed into the impeller is deflected by 90° andis ejected toward the radially outer side of the impeller.

The known impeller has a problem in that turbulence may occur near theradially inner ends of the blades. Consequently, the air-sendingefficiency of the impeller may be reduced.

SUMMARY OF THE INVENTION

An impeller according to an exemplary embodiment of the presentdisclosure rotates on a center axis extending in a vertical direction.The impeller includes a main plate spreading radially with respect tothe center axis, a plurality of blades provided on an upper surface ofthe main plate and arranged side by side in a circumferential direction,a shroud connected to tops of the plurality of blades and having anintake port that is an opening extending upward, and a mount portionprovided on the upper surface of the main plate and positioned on aninner side with respect to a radially outer end of the main plate. Themount portion has a plurality of recesses each being depressed downwardfrom an upper surface of the mount portion and extending in a directionaway from the center axis.

The above and other elements, features, steps, characteristics andadvantages of the present disclosure will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall perspective view of an exemplary cleaning machineaccording to an embodiment of the present disclosure.

FIG. 2 is an overall perspective view of an air-sending apparatusincluded in the cleaning machine according to the embodiment of thepresent disclosure.

FIG. 3 is a vertical sectional view of the air-sending apparatusaccording to the embodiment of the present disclosure.

FIG. 4 is a vertical sectional view of an impeller included in theair-sending apparatus according to the embodiment of the presentdisclosure.

FIG. 5 is a top view of the impeller according to the embodiment of thepresent disclosure.

FIG. 6 is an enlarged top view of a part of the impeller according tothe embodiment of the present disclosure.

FIG. 7 is a top view of the impeller according to the embodiment of thepresent disclosure, with a shroud thereof removed.

FIG. 8 is a vertical sectional perspective view of the impelleraccording to the embodiment of the present disclosure.

FIG. 9 is a perspective view of a washer included in the impelleraccording to the embodiment of the present disclosure.

FIG. 10 is a top view of an impeller according to a first modificationof the embodiment of the present disclosure, with a shroud thereofremoved.

FIG. 11 is a top view of a washer included in an impeller according to asecond modification of the embodiment of the present disclosure.

FIG. 12 is a vertical sectional view of a part of the washer included inthe impeller according to the second modification of the embodiment ofthe present disclosure.

FIG. 13 is a vertical sectional view of a washer include in an impelleraccording to a third modification of the embodiment of the presentdisclosure.

FIG. 14 is a vertical sectional view of an impeller according to afourth modification of the embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the present disclosure will now be described indetail with reference to the drawings. Herein, a direction in which acenter axis of an impeller extends is simply referred to as “the axialdirection,” a direction spreading from and being orthogonal to thecenter axis of the impeller is simply referred to as “the radialdirection,” and a direction in which an arc centered on the center axisof the impeller extends is simply referred to as “the circumferentialdirection.” A center axis of an air-sending apparatus coincides with thecenter axis of the impeller. Herein, as a matter of convenience indescription, the axial direction is regarded as the vertical direction,and shapes and relative positions of relevant elements will be describedon the basis of a definition that the vertical direction in FIGS. 3 and4 corresponds to the vertical direction of the impeller and theair-sending apparatus. “The upper side” of the impeller and theair-sending apparatus corresponds to “the intake side,” and “the lowerside” of the impeller and the air-sending apparatus corresponds to “theexhaust side.” The above definition of the vertical direction does notlimit the orientations and the relative positions of the impeller andthe air-sending apparatus at the time of use.

Herein, shapes and relative positions of elements included in a cleaningmachine will be described on the basis of a definition that a side ofthe cleaning machine nearer to the floor surface corresponds to “thelower side,” and a side of the cleaning machine farther from the floorsurface corresponds to “the upper side.” The definition of the sides donot limit the orientation and the relative position of the cleaningmachine at the time of use. The relative positions of relevant elementsmay also be described by using the terms “the upstream side” and “thedownstream side” in the direction in which air flows from the intakeside toward the exhaust side at the activation of the air-sendingapparatus. The terms “parallel” and “perpendicular” used herein do notnecessarily mean exactly parallel and exactly perpendicular but implysubstantially parallel and substantially perpendicular, respectively.

FIG. 1 is an overall perspective view of an exemplary cleaning machine100 according to an embodiment of the present disclosure. The cleaningmachine 100 is a so-called stick-type electric cleaning machine andincludes a casing 102 having an intake part 103 and an exhaust part 104that are openings provided in the lower surface and in the upper surfacethereof, respectively. The casing 102 is provided with a power cord (notillustrated) drawn from one surface thereof. The power cord is connectedto a power socket (not illustrated) provided on a wall of a room andthus supplies power to the cleaning machine 100. The cleaning machine100 may alternatively be a so-called robot-type, canister-type, orhandy-type electric cleaning machine.

The casing 102 has thereinside with an air passage (not illustrated)that connects the intake part 103 and the exhaust part 104 to eachother. The air passage is provided thereinside with a dust-collectingportion (not illustrated), a filter (not illustrated), and anair-sending apparatus 1 in that order from the upstream side toward thedownstream side in the direction of airflow. Dust such as dirt particlescontained in the air flowing through the air passage is collected by thefilter and is stored in the dust-collecting portion, which has acontainer-like shape. Thus, the cleaning machine 100 can clean a floorsurface F. The dust-collecting portion and the filter are detachablyattached to the casing 102.

The casing 102 is provided in an upper part thereof with a grip portion105 and an operation portion 106. The user can hold the grip portion 105and thus move the cleaning machine 100. The operation portion 106includes a plurality of buttons 106 a. The user operates the buttons 106a to make instructions and settings for the operation of the cleaningmachine 100. For example, with the operation of a relevant one of thebuttons 106 a, an instruction for the activation of the air-sendingapparatus 1, the stopping of the air-sending apparatus 1, a change inthe rotation speed of the air-sending apparatus 1, or the like can bemade.

The intake part 103 receives the downstream end of a suction pipe 107(the upper end of the suction pipe 107 in FIG. 1) connected thereto. Thesuction pipe 107 extends substantially linearly. The upstream end of thesuction pipe 107 (the lower end of the suction pipe 107 in FIG. 1) isprovided with a suction nozzle 110 detachably attached thereto.

FIG. 2 is an overall perspective view of the air-sending apparatus 1included in the cleaning machine 100 according to the embodiment of thepresent disclosure. FIG. 3 is a vertical sectional view of theair-sending apparatus 1 according to the embodiment of the presentdisclosure. Roughly speaking, the air-sending apparatus 1 includes a fancasing 2, an impeller 3, a motor 4, and a substrate 5. When the impeller3 is driven to rotate by the motor 4, air is taken into the fan casing 2from the upper side (the upper side in FIG. 3) of the air-sendingapparatus 1 and is exhausted from the lower end of the fan casing 2toward the lower side (the lower side in FIG. 3). Seen from the upperside in the axial direction, the impeller 3 rotates counterclockwise.

The fan casing 2 is a cylinder whose section taken in the radialdirection has a substantially circular shape. The fan casing 2 housesthe impeller 3 and the motor 4. The fan casing 2 includes an upper case21 and a lower case 22.

The upper case 21 has a substantially circular cylindrical shape withthe lower side thereof being open. The upper case 21 covers the impeller3. The lower case 22 has a substantially circular cylindrical shape withthe upper side and the lower side thereof being open. The lower case 22covers the motor 4. The lower end of the upper case 21 and the upper endof the lower case 22 are connected to each other, whereby the internalspaces of the two become continuous with each other. The upper case 21and the lower case 22 may be provided separately from each other asdescribed above or integrally with each other.

The upper case 21 has an intake port 211 at the upper end thereof. Theintake port 211 is an opening extending in the vertical direction. Theintake port 211 is positioned on the upper side with respect to theupper end of the impeller 3. The inside diameter of the intake port 211is smaller than the inside diameter of the upper case 21. The lower case22 has an exhaust port 221 at the lower end thereof. The exhaust port221 is an opening extending in the vertical direction. The exhaust port221 is defined between the inner surface of the lower case 22 and amotor housing 41 to be described below. In the cleaning machine 100, theair-sending apparatus 1 is oriented such that the intake port 211thereof faces downward.

The impeller 3 is positioned inside the upper case 21 of the fan casing2. The impeller 3 is fixed to a shaft 431, to be described below, of themotor 4. The impeller 3 rotates on a center axis C extending in thevertical direction.

When the impeller 3 is driven to rotate by the motor 4, air is takenfrom the intake port 211 of the upper case 21 into the impeller 3. Theair thus taken into the impeller 3 is guided toward the radially outerside by the impeller 3 and is further blown toward the radially outerside of the impeller 3. Details of the impeller 3 will be describedseparately below.

The motor 4 is positioned inside the lower case 22 of the fan casing 2.Roughly speaking, the motor 4 includes the motor housing 41, a stator42, and a rotor 43.

The motor housing 41 includes an upper housing 411 and a lower housing412. The upper housing 411 has a substantially circular cylindricalshape with the lower side thereof being open. The lower housing 412 hasa substantially circular cylindrical shape with the upper side thereofbeing open. The lower end of the upper housing 411 and the upper end ofthe lower housing 412 are connected to each other, whereby the internalspaces of the two become continuous with each other. The upper housing411 and the lower housing 412 are fixed to each other with screws 41Aprovided at predetermined intervals in the circumferential direction.The motor housing 41 houses the stator 42 and the rotor 43.

The upper housing 411 includes a bearing-holding portion 4111 in aradially central part of the upper surface thereof. The bearing-holdingportion 4111 is depressed downward from the upper surface of the upperhousing 411 and is a concavity having a circular shape when sectioned inthe radial direction. The bearing-holding portion 4111 has a hole 4111Ain the center of the inner bottom thereof. The hole 4111A extends in thevertical direction along the center axis C through the bottom of thebearing-holding portion 4111. The bearing-holding portion 4111 receivesan upper bearing 44 fixedly fitted therein from the upper side. Theupper bearing 44 is, for example, a ball bearing. Alternatively, theupper bearing 44 may be a sleeve bearing or the like.

The upper housing 411 is provided with a plurality of stator vanes 4112on the outer circumferential surface thereof. The plurality of statorvanes 4112 are arranged at predetermined intervals in thecircumferential direction and each extend in the vertical direction. Anupper portion of each of the stator vanes 4112 is curved toward thebackward side in the direction of rotation of the impeller 3 withrespect to a lower portion of the stator vane 4112. The air blown fromthe impeller 3 that is rotating is guided between circumferentiallyadjacent ones of the stator vanes 4112 from the upper side toward thelower side. Thus, air currents can be rectified.

The lower housing 412 has an attaching hole 412A in a central part ofthe lower surface thereof. The attaching hole 412A extends in thevertical direction through the lower surface of the lower housing 412.The attaching hole 412A receives a bracket 45 fitted therein from thelower side and fixed thereto with screws (not illustrated).

The bracket 45 includes a bearing-holding portion 451 in a radiallycentral part of the upper surface thereof. The bearing-holding portion451 is depressed downward from the upper surface of the bracket 45 andis a concavity having a circular shape when sectioned in the radialdirection. The bearing-holding portion 451 has a hole 451A in the centerof the inner bottom thereof. The hole 451A extends in the verticaldirection along the center axis C through the bottom of thebearing-holding portion 451. The bearing-holding portion 451 receives alower bearing 46 fixedly fitted therein from the upper side. The lowerbearing 46 is, for example, a ball bearing. Alternatively, the lowerbearing 46 may be a sleeve bearing or the like.

The stator 42 is positioned on the radially inner side of the innercircumferential surface of the motor housing 41. The stator 42 includesa stator core 421, a plurality of coils 422, and an insulator 423.

The stator core 421 is obtained by stacking electromagnetic steel sheetsin the vertical direction. The stator core 421 includes an annular coreback 4211 and a plurality of teeth 4212. The plurality of teeth 4212extend from the inner circumferential surface of the core back 4211toward the radially inner side. The teeth 4212 each have a substantiallyT shape when seen from either side in the axial direction. The pluralityof coils 422 are each formed of a conducting wire wound around acorresponding one of the teeth 4212 with the insulator 423, having aninsulating characteristic, interposed therebetween. A lead wire 422A isdrawn downward from each of the coils 422. The lead wire 422A iselectrically connected to the substrate 5.

The inner circumferential surface and the outer circumferential surfaceof the core back 4211 are flat in areas near the roots of the respectiveteeth 4212. Thus, the collapsing of the coils 422 can be suppressed. Inthe other areas excluding the areas near the roots of the respectiveteeth 4212, the inner circumferential surface and the outercircumferential surface of the core back 4211 are curved. The curvedportions of the outer circumferential surface of the core back 4211 arein contact with the inner circumferential surface of the motor housing41.

The rotor 43 is positioned on the radially inner side of the stator 42.The rotor 43 is rotatable on the center axis C relative to the stator42. The rotor 43 includes the shaft 431 and a magnet 432.

The shaft 431 extends along the center axis C. The shaft 431 issupported by the upper bearing 44 and the lower bearing 46 in such amanner as to be rotatable relative to the motor housing 41. The magnet432 has a cylindrical shape and is fixed to the shaft 431 extendingtherethrough. The outer circumferential surface of the magnet 432 iscovered with a rotor cover (not illustrated). The magnet 432 and therotor cover are positioned on the radially inner side of the teeth 4212and face the teeth 4212 in the radial direction.

The substrate 5 has a disc-like shape spreading radially with respect tothe center axis C. The substrate 5 is positioned on the lower side withrespect to the lower housing 412 and the bracket 45. The substrate 5 isfixed to the lower housing 412 with screws 52 with a plurality ofspacers 51 interposed therebetween. The spacers 51 are positioned on thelower side of the lower housing 412 and are arranged side by side in thecircumferential direction.

The substrate 5 is a rigid substrate or a flexible substrate. The leadwires 422A drawn from the respective coils 422 of the motor 4 areelectrically connected to a driving circuit (not illustrated) mounted onthe substrate 5. Thus, power can be supplied to the coils 422.

FIG. 4 is a vertical sectional view of the impeller 3 included in theair-sending apparatus 1 according to the embodiment of the presentdisclosure. FIG. 5 is a top view of the impeller 3 according to theembodiment of the present disclosure. FIG. 6 is an enlarged top view ofa part of the impeller 3 according to the embodiment of the presentdisclosure. FIG. 7 is a top view of the impeller 3 according to theembodiment of the present disclosure, with a shroud 33 thereof removed.FIG. 8 is a vertical sectional perspective view of the impeller 3according to the embodiment of the present disclosure. FIG. 9 is aperspective view of a washer 34 included in the impeller 3 according tothe embodiment of the present disclosure. In FIGS. 5 to 11, thedirection of rotation of the impeller 3 is represented by an arrow R.

The impeller 3 is a metal member, for example, and has a circular shapewhen seen in the axial direction. The impeller 3 includes a main plate31, a plurality of blades 32, the shroud 33, and a mount portion. In thepresent embodiment, the mount portion corresponds to the washer 34.

The main plate 31 is positioned at the bottom of the impeller 3. Themain plate 31 spreads radially with respect to the center axis C. Themain plate 31 is a disc-like member. The main plate 31 has a hole 31Aextending in the vertical direction along the center axis C through thecenter thereof. The main plate 31 supports the bottoms of the blades 32.

The plurality (for example, fourteen) of blades 32 are positioned on theupper surface of the main plate 31 and are arranged thereon side by sidein the circumferential direction. The bottoms of the respective blades32 are connected to the main plate 31. The tops of the respective blades32 are connected to the shroud 33.

The blades 32 are each a plate-like member standing in the verticaldirection and extending from the radially inner side toward the radiallyouter side. Seen in the axial direction, the blades 32 are each curvedin such a manner as to be convex toward the forward side in thedirection of rotation R, with the radially inner end thereof beingpositioned on the forward side in the direction of rotation R withrespect to the radially outer end thereof.

The plurality of blades 32 are of two kinds: first blades 32A and secondblades 32B that are provided in the same number (seven each, forexample). Herein, the first blades 32A and the second blades 32B mayalso be generally denoted as “the blades 32” unless they need to bedistinguished from each other.

The length of the first blades 32A in the radial direction is greaterthan the length of the second blades 32B in the radial direction. Theradially outer ends of the first blades 32A and the radially outer endsof the second blades 32B substantially coincide with the radially outerend (the outer circumferential edge) of the main plate 31. The radiallyinner ends of the first blades 32A are positioned near the radiallyouter end of the washer 34 to be described below. The radially innerends of the second blades 32B are positioned near the midpoint betweenthe center axis C and the radially outer end of the main plate 31.Therefore, the air passage between circumferentially adjacent ones ofthe first blades 32A is divided near the midpoint in the direction ofairflow (the radial direction) by a corresponding one of the secondblades 32B into a passage on the forward side in the direction ofrotation R and a passage on the backward side in the direction ofrotation R.

In an upstream portion of the impeller 3 in the direction of airflow,air passes through a gap between the radially inner ends ofcircumferentially adjacent ones of the first blades 32A and flows towardthe radially outer side of the main plate 31. The air that has passedthrough the gap between the radially inner ends of the circumferentiallyadjacent ones of the first blades 32A is divided by the correspondingsecond blade 32B, before reaching the radially outer end of the mainplate 31, into an airflow on the forward side in the direction ofrotation R and an airflow on the backward side in the direction ofrotation R.

The shroud 33 is positioned over the plurality of blades 32. Seen in theaxial direction, the shroud 33 is an annular plate member with theradially inner end and the radially outer end thereof being circular. Aportion of the shroud 33 that is on the radially outer side with respectto the substantial midpoint of the shroud 33 between the radially innerend and the radially outer end extends parallel to the main plate 31with a gap therebetween in the axial direction. A portion of the shroud33 that is on the radially inner side is curved upward. The shroud 33has an intake port 331 that is an opening extending upward (in aradially central part thereof). A portion of the shroud 33 around theintake port 331 has a cylindrical shape. The shroud 33 supports the topsof the respective blades 32. That is, the shroud 33 is connected to thetops of the plurality of blades 32 and has the intake port 331 as anopening extending upward.

In the impeller 3, the upper end of each of the first blades 32A extendsfrom the radially outer end to the radially inner end of the shroud 33along the lower surface of the shroud 33. The upper end of each of thefirst blades 32A has a highest part 32Aa immediately below the radiallyouter end of the intake port 331, i.e., immediately below the inner endof the shroud 33. The upper end of each of the first blades 32A smoothlydescends from the highest part 32Aa toward the radially inner side andeventually reaches the upper surface of the main plate 31 at theradially inner end.

The washer 34 is provided on the upper surface of the main plate 31 andis positioned on the inner side with respect to the radially outer endof the main plate 31. The washer 34 is a disc-like member having apredetermined height from the upper surface of the main plate 31 andspreading radially with respect to the center axis C. The washer 34 hasa boss 34A projecting upward at the center thereof. The boss 34A has ahole 34B in the center thereof. The hole 34B extends in the verticaldirection along the center axis C through the boss 34A.

The impeller 3 is fixed to the shaft 431 at the main plate 31 and thewasher 34 thereof.

As illustrated in FIG. 3, a spacer 471 is provided above the upperbearing 44 and below the main plate 31. The spacer 471 is fixed to theshaft 431. The shaft 431 is made to pass through the hole 31A of themain plate 31, whereby the impeller 3 is positioned on the upper surfaceof the spacer 471. Subsequently, the shaft 431 is made to pass throughthe hole 34B of the washer 34, whereby the washer 34 is positioned onthe upper surface of the main plate 31. Then, a fixing member, such as anut 472, is screwed onto the upper end of the shaft 431 with the mainplate 31 and the washer 34 being held between the spacer 471 and the nut472. Thus, the impeller 3 is fixed to the shaft 431 with the nut 472.

Referring now to FIG. 9, the washer 34 includes an outer circumferentialportion 34C on the radially outer side with respect to the boss 34A. Theupper surface of the outer circumferential portion 34C is parallel tothe upper surface of the main plate 31. The outer circumferentialportion 34C has a plurality of recesses 34D.

The recesses 34D are each depressed downward from the upper surface ofthe outer circumferential portion 34C. The recesses 34D each extend in adirection away from the center axis C. Specifically, the recesses 34Dare each a groove having a rectangular shape when sectioned in the axialdirection. The recesses 34D each have a side surface 34Da on the forwardside in the direction of rotation R, and a side surface 34Db on thebackward side in the direction of rotation R. The side surfaces 34Da and34Db each extend in the vertical direction parallel to the center axisC. The plurality (for example, seven) of recesses 34D provided in theupper surface of the outer circumferential portion 34C are arranged sideby side in the circumferential direction. That is, the washer 34 has therecesses 34D each being depressed downward from the upper surfacethereof and extending in the direction away from the center axis C.

Since the washer 34 has the recesses 34D as described above, theoccurrence of turbulence near the radially inner ends of the blades 32can be suppressed. If the washer 34 has no recesses 34D, some of the airtaken from the intake port 331 may flow toward the radially inner sidewhen flowing near the radially outer side of hills 34E to be describedbelow. Consequently, turbulence may occur near the radially outer sideof the hills 34E. In contrast, since the washer 34 according to thepresent embodiment has the recesses 34D, when the impeller 3 is rotated,the recesses 34D generate air currents flowing toward the radially outerside. Therefore, the occurrence of radially inward flow of the air nearthe radially outer side of the hills 34E can be suppressed. Hence, theimpeller 3 configured as above can exhibit improved air-sendingefficiency.

As illustrated in FIG. 9, seen in the axial direction, the recesses 34Dare each curved in such a manner as to be convex toward the forward sidein the direction of rotation R, with the radially inner end thereofbeing positioned on the forward side in the direction of rotation R withrespect to the radially outer end thereof. That is, the radially innerend of each recess 34D is positioned on the forward side in thedirection of rotation R of the impeller 3 with respect to the radiallyouter end of the recess 34D. Hence, when the impeller 3 is rotated, therecesses 34D can more easily generate the air currents flowing towardthe radially outer side. Therefore, the occurrence of turbulence nearthe radially inner ends of the blades 32 can be suppressed effectively.

The recesses 34D are each concave by a predetermined depth from theupper surface of the outer circumferential portion 34C. That is, thebottom surface of each recess 34D at the radially outer end of therecess 34D is positioned above the upper surface of the main plate 31.In such a relationship, if the height in the recess 34D, i.e., the depthof the recess 34D, is adjusted, the effect of suppressing the occurrenceof turbulence can be increased.

As illustrated in FIG. 9, the washer 34 includes the plurality of hills34E provided in correspondence with the plurality of recesses 34Darranged side by side in the circumferential direction. The plurality ofhills 34E are each positioned between circumferentially adjacent ones ofthe plurality of recesses 34D. The hills 34E project upward with respectto the recesses 34D. That is, the washer 34 has the plurality ofrecesses 34D arranged side by side in the circumferential direction, andthe plurality of hills 34E each provided between circumferentiallyadjacent ones of the recesses 34D and projecting upward with respect tothe recesses 34D. A circumferential length L1 of each recess 34D at theradially outer end is smaller than a circumferential length L2 of eachhill 34E at the radially outer end. Since the circumferential length L1of the recess 34D at the radially outer end, i.e., the width of therecess 34D in the form of a groove, is set smaller than thecircumferential length L2 of the hill 34E as described above, theoccurrence of backward flow of the air toward the radially inner sidecan be suppressed more than in a case where the recess 34D has a greaterwidth.

Referring now to FIG. 6, the washer 34 is positioned on the radiallyinner side with respect to the radially inner ends of the first blades32A. There is a predetermined distance between the radially outer end ofthe washer 34 and the radially inner end of each of the first blades32A. Specifically, a distance D1 from the center axis C to the radiallyouter end of the washer 34 is smaller than a distance D2 from the centeraxis C to the radially inner end of each of the first blades 32A. Insuch a relationship, the radially inner ends of the first blades 32A arenot positioned on the radially inner side with respect to the radiallyouter end of the washer 34. Thus, the narrowing of air passages near theradially inner ends of the blades 32 can be suppressed, and theoccurrence of turbulence can be suppressed.

As illustrated in FIG. 6, a circumferential opening angle G1 of each ofthe recesses 34D at the radially outer end with respect to the centeraxis C is smaller than a circumferential angle G2 formed between theradially inner ends of circumferentially adjacent ones of the firstblades 32A with respect to the center axis C. Since the circumferentialopening angle G1 of each recess 34D at the radially outer end, that is,the width of the recess 34D in the form of a groove, is set smaller thanthe interval between adjacent ones of the blades 32 as described above,the occurrence of backward flow of the air toward the radially innerside can be suppressed.

As illustrated in FIG. 6, seen in the axial direction, the washer 34 ispositioned on the radially inner side with respect to the radially outerend of the intake port 331. Specifically, the distance D1 from thecenter axis C to the radially outer end of the washer 34 is smaller thana distance D3 from the center axis C to the radially outer end of theintake port 331. In such a relationship, the outside diameter of thewasher 34 is reduced. Therefore, the weight of the impeller 3 can bereduced. Moreover, the occurrence of turbulence near the radially innerends of the blades 32 can be suppressed. That is, the narrowing of apassage of the air taken from the intake port 331 into the impeller 3can be suppressed more than in a case where the radially outer end ofthe washer 34 is positioned on the outer side with respect to theradially outer end of the intake port 331. Therefore, the occurrence ofturbulence can be suppressed.

Referring now to FIG. 4, a height H1 of the washer 34 at the radiallyouter end thereof is smaller than a height H2 of each first blade 32A onthe radially inner side thereof. In the present embodiment, the heightH2 refers to the height of the first blade 32A at the highest part 32Aadefined in a portion of the first blade 32A that is on the radiallyinner side thereof. In such a relationship, the narrowing of the airpassage on the radially inner side of each of the blades 32 can besuppressed more than in a case where the height H1 of the washer 34 atthe radially outer end thereof is greater than the height H2 of thefirst blade 32A on the radially inner side thereof. Furthermore, theoccurrence of turbulence can be suppressed.

The washer 34 is a member provided separately from the main plate 31.The lower surface of the washer 34 is in contact with the upper surfaceof the main plate 31. The upper surface of the washer 34 is in contactwith the lower surface of the fixing member. The fixing membercorresponds to the nut 472, for example. The impeller 3 is configuredsuch that the main plate 31 is fixed to the shaft 431, which isrotatable on the center axis C, with the fixing member. In such aconfiguration, since the member having the recesses 34D is the washer34, not only the occurrence of turbulence can be suppressed, but alsothe strength of fixing the impeller 3 to the shaft 431 can be increased.

The air-sending apparatus 1 includes the impeller 3. In the aboveconfiguration according to the present embodiment, the occurrence ofturbulence in the impeller 3 included in the air-sending apparatus 1 canbe suppressed. Accordingly, the air-sending apparatus 1 can exhibitimproved air-sending efficiency. The cleaning machine 100 includes theair-sending apparatus 1. Therefore, the occurrence of turbulence in theair-sending apparatus 1 included in the cleaning machine 100 can besuppressed. Accordingly, the cleaning machine 100 can exhibit improvedperformance in suction.

FIG. 10 is a top view of an impeller 3 according to a first modificationof the embodiment of the present disclosure, with a shroud 33 thereofremoved.

As illustrated in FIG. 10, the impeller 3 includes a plurality (forexample, seven) of blades 32. The radially outer ends of the blades 32substantially coincide with the radially outer end (the outercircumferential edge) of the main plate 31. The radially inner ends ofthe blades 32 are positioned near the radially outer end of the washer34. The impeller 3 according to the first modification illustrated inFIG. 10 includes no second blades 32B, unlike the impeller 3 describedabove with reference to FIGS. 4 to 9.

Letting the number of recesses 34D be N1 and the number of blades 32 beN2, a value expressed by N1/N2 preferably falls within a range from 0.5to 1.2. More preferably, (N1/N2) is about 1.0.

In the impeller 3 described with reference to FIGS. 4 to 9, N1 as thenumber of recesses 34D is 7, and N2 as the number of blades 32 is 14.Accordingly, (N1/N2) is 0.5. In the impeller 3 according to the firstmodification illustrated in FIG. 10, N1 as the number of recesses 34D is7, and N2 as the number of blades 32 is 7. Accordingly, (N1/N2) is 1.0.

Since the number of recesses 34D and the number of blades 32 are set onthe basis of the above predetermined relationship, the occurrence ofturbulence near the radially inner ends of the blades 32 can further besuppressed. In particular, since the impeller 3 according to the firstmodification is configured such that (N1/N2)=1.0, the occurrence ofturbulence near the radially inner ends of the blades 32 can besuppressed much more effectively.

FIG. 11 is a top view of a washer 34 included in an impeller 3 accordingto a second modification of the embodiment of the present disclosure.FIG. 12 is a vertical sectional view of a part of the washer 34 includedin the impeller 3 according to the second modification of the embodimentof the present disclosure. The section illustrated in FIG. 12 is takenalong line XII-XII illustrated in FIG. 11.

As illustrated in FIGS. 11 and 12, the recesses 34D each have arectangular shape when sectioned in the axial direction. The recesses34D each have a side surface 34Da provided on the forward side thereofin the direction of rotation R, and a side surface 34Db provided on thebackward side thereof in the direction of rotation R.

The side surface 34Da of each recess 34D that is on the forward side inthe direction of rotation R includes a recess-widening part 34Dc. Therecess-widening part 34Dc is provided in an upper part of the sidesurface 34Da. The lower end of the recess-widening part 34Dc, i.e., aconnecting part between the recess-widening part 34Dc and the sidesurface 34Da, extends parallel to the center axis C. The recess-wideningpart 34Dc extends upward while inclining toward the forward side in thedirection of rotation R such that the recess 34D is widened. In thepresent embodiment, the recess-widening part 34Dc is a curved surface.In such a shape, the occurrence of turbulence near the upper end of theside surface 34Da of the recess 34D that is on the forward side in thedirection of rotation R can be suppressed. More specifically, forexample, if the recesses 34D each have no recess-widening part 34Dc andif the side surface 34Da of the recess 34D that is on the forward sidein the direction of rotation R extends parallel to the center axis C andis connected substantially orthogonally to a corresponding one of thehills 34E, air flowing with the rotation of the impeller 3 from theforward side in the direction of rotation R toward the side surface 34Daon the forward side in the direction of rotation R may be separated fromthe side surface 34Da near the upper end of the side surface 34Da,causing turbulence. In contrast, according to the present embodiment,since the recesses 34D each have the recess-widening part 34Dc, theoccurrence of such turbulence can be suppressed.

The recess-widening part 34Dc is not limited to a curved surface and maybe a flat surface that is inclined at a predetermined angle with respectto the center axis C.

The side surface 34Db of each recess 34D that is on the backward side inthe direction of rotation R extends parallel to the center axis C. Sincethe side surface 34Db on the backward side in the direction of rotationR extends in the vertical direction, when the impeller 3 is rotated, aircan be efficiently exhausted toward the radially outer side. That is,air near the upper end of the side surface 34Db on the backward side inthe direction of rotation R can be more efficiently exhausted toward theradially outer side than in a case where an upper part of the sidesurface 34Db on the backward side in the direction of rotation R iscurved toward the backward side in the direction of rotation R withrespect to the center axis C.

FIG. 13 is a vertical sectional view of a washer 34 include in animpeller 3 according to a third modification of the embodiment of thepresent disclosure.

As illustrated in FIG. 13, the washer 34 includes an inclined part 34Cawhose upper surface descends toward the radially outer side. Morespecifically, the washer 34 includes an outer circumferential portion34C. The outer circumferential portion 34C includes the inclined part34Ca whose upper surface descends toward the radially outer side. Theinclined part 34Ca is tapered from the side thereof nearer to the centeraxis C. In such a shape, a reduction in the distance between the uppersurface of the washer 34 and the lower surface of the shroud 33 in adirection from the center axis C toward the radially outer side can besuppressed. That is, the narrowing of the air passage can be suppressed.

FIG. 14 is a vertical sectional view of an impeller 3 according to afourth modification of the embodiment of the present disclosure.

As illustrated in FIG. 14, the main plate 31 includes a mount portion31B. The mount portion 31B is a part of the main plate 31. Except thatthe mount portion 31B is a part of the main plate 31, the mount portion31B has the same configuration as the washer 34 described above.Specifically, the mount portion 31B includes a boss 31Ba, an outercircumferential part 31Bc, recesses 31Bd, and hills 31Be. In such aconfiguration, the number of components included in the impeller 3 canbe reduced, and the efficiency in the work of assembling the impeller 3can be improved.

The air-sending apparatus 1 may be included not only in a cleaningmachine but also in any of various office automation apparatuses,medical apparatuses, and transport apparatuses, or any of home electricapparatuses other than the cleaning machine.

The present disclosure is applicable to, for example, an air-sendingapparatus intended for a cleaning machine.

Features of the above-described preferred embodiments and themodifications thereof may be combined appropriately as long as noconflict arises.

While preferred embodiments of the present disclosure have beendescribed above, it is to be understood that variations andmodifications will be apparent to those skilled in the art withoutdeparting from the scope and spirit of the present disclosure. The scopeof the present disclosure, therefore, is to be determined solely by thefollowing claims.

What is claimed is:
 1. An impeller that rotates on a center axisextending in a vertical direction, the impeller comprising: a main platespreading radially with respect to the center axis; a plurality ofblades provided on an upper surface of the main plate and arranged sideby side in a circumferential direction; a shroud connected to tops ofthe plurality of blades and having an intake port that is an openingextending upward; and a mount portion provided on the upper surface ofthe main plate and positioned on an inner side with respect to aradially outer end of the main plate, wherein the mount portion has aplurality of recesses each being depressed downward from an uppersurface of the mount portion and extending in a direction away from thecenter axis.
 2. The impeller according to claim 1, wherein a radiallyinner end of each of the recesses is positioned on a forward side in adirection of rotation of the impeller with respect to a radially outerend of the recess.
 3. The impeller according to claim 1, wherein a sidesurface of each of the recesses that is on the forward side in thedirection of rotation includes a recess-widening part extending upwardwhile inclining toward the forward side in the direction of rotationsuch that the recess is widened.
 4. The impeller according to claim 1,wherein a side surface of each of the recesses that is on a backwardside in the direction of rotation extends parallel to the center axis.5. The impeller according to claim 1, wherein a distance from the centeraxis to a radially outer end of the mount portion is smaller than adistance from the center axis to a radially inner end of each of theblades.
 6. The impeller according to claim 1, wherein the distance fromthe center axis to the radially outer end of the mount portion issmaller than a distance from the center axis to a radially outer end ofthe intake port.
 7. The impeller according to claim 1, wherein a heightof the mount portion at the radially outer end of the mount portion issmaller than a height of each of the blades on a radially inner side ofthe blade.
 8. The impeller according to claim 1, wherein the mountportion includes the plurality of recesses arranged side by side in thecircumferential direction; and hills each provided betweencircumferentially adjacent ones of the recesses and projecting upwardwith respect to the recesses, and wherein a circumferential length ofeach of the recesses at the radially outer end of the recess is smallerthan a circumferential length of each of the hills at a radially outerend of the hill.
 9. The impeller according to claim 1, wherein acircumferential opening angle of each of the recesses at the radiallyouter end of the recess with respect to the center axis is smaller thana circumferential angle formed between the radially inner ends ofcircumferentially adjacent ones of the blades with respect to the centeraxis.
 10. The impeller according to claim 1, wherein a bottom surface ofeach of the recesses at the radially outer end of the recess ispositioned above the upper surface of the main plate.
 11. The impelleraccording to claim 1, wherein the mount portion includes an inclinedpart whose upper surface descends toward the radially outer side of themount portion.
 12. The impeller according to claim 1, wherein, letting anumber of recesses be N1 and a number of blades be N2, a value expressedby N1/N2 falls within a range from 0.5 to 1.2.
 13. The impelleraccording to claim 1, wherein the main plate is fixed to a shaft with afixing member, the shaft being rotatable on the center axis, wherein themount portion is provided separately from the main plate, wherein alower surface of the mount portion is in contact with the upper surfaceof the main plate, and wherein the upper surface of the mount portion isin contact with a lower surface of the fixing member.
 14. The impelleraccording to claim 1, wherein the mount portion is a part of the mainplate.
 15. An air-sending apparatus comprising: the impeller accordingto claim
 1. 16. A cleaning machine comprising: the air-sending apparatusaccording to claim 15.